In a current transport network, when network traffic is to be switched at an intermediate node, first, optical-to-electrical conversion needs to be performed on the network traffic, after the conversion to an electrical domain, electrical switching is performed, and after the switching, electrical-to-optical conversion is performed so that the network traffic is converted back into an optical signal for transmission. The optical-to-electrical-to-optical conversion and the electrical switching in the entire process bring huge additional power consumption and costs to the network. To decrease the power consumption and costs, an all-optical switching technology is proposed. In all-optical switching, network data is carried in a form of an optical burst packet, and therefore at a switching node, switching can be directly completed in an optical domain, and only an optical switching device needs to be retained at the node, which can save a large quantity of optical-to-electrical-to-optical conversion and electrical switching devices, and greatly reduce power consumption and costs of a network.
To support the all-optical switching technology, an optical transceiver in a network is required to be capable of transmitting and receiving an optical signal in a burst form. As a requirement on a network capacity becomes increasingly high, a current commercial 10 G burst optical module using an OOK (On-Off Keying) modulation format cannot meet the requirement, and a high-speed burst receiving and transmitting technology based on a coherence technology begins to be developed in the industry. A hardware structure of a high-speed burst optical module is basically consistent with that of a current commercial continuous-mode coherent optical module, and a main difference lies in a DSP (digital signal processing, Digital Signal Processing) algorithm. For features that a burst signal lasts for a short time and each burst packet has a different characteristic, when a burst DSP algorithm is used, signal demodulation needs to be quickly completed; therefore, most algorithm modules are implemented based on a training sequence, and all are forward algorithms that do not include feedbacks.
In an all-optical switching network, in transferring and switching of an optical burst packet, a format of data carried in the optical burst packet is transparent, and therefore nodes in the network may transmit burst packets in different modulation formats, for example, some transmit burst packets in a QPSK (Quadrature Phase Shift Keying, quadrature phase shift keying) format, and some transmit burst packets in a 16QAM (16 Quadrature Amplitude Modulation, quadrature amplitude modulation in which 16 symbols are included) format, which requires a burst receiver to be capable of supporting receiving and demodulation of burst signals in multiple modulation formats.
The prior art discloses a coherent burst receiver BMR. In the BMR, channel equalization is still implemented by using a constant modulus algorithm CMA that is commonly used in continuous receivers, and only corresponding improvement is made for a burst signal to increase a convergence speed. Because the CMA algorithm is applicable to only an equal-amplitude modulation format (for example, m-PSK), the BMR cannot support receiving of a non-equal-amplitude QAM signal.